The present invention relates to a standalone machine for the preparation of drinks, or other similar products, by the extraction under pressure of a food substance contained in a capsule. The invention relates more precisely to mobile or portable coffee machines using extraction capsules.
Drink preparation machines, of the coffee machine type, which use packaged portions of food substance are rapidly becoming widespread in homes or even in communal premises, commercial places or companies. The preparation principle is based on the extraction of portions containing a food substance (ground coffee for example) by passing though this portion a quantity of cold or hot liquid under high pressure, typically a pressure several times higher than atmospheric pressure. The packaged portions can be partially rigid capsules or flexible sachets, sealed or partially open, or filter pods.
An example of a capsule is described in the European patent application EP 0 512 468 B1. An example of a sachet is described in the European patent application EP 0 602 203 B1. Other examples of capsules are described in PCT application WO 03/059778 and European patent applications EP 1 344 722 and EP 1 440 905.
Such extraction systems have many advantages. On the one hand, the individual packages are easy to use and do not require manual measuring of coffee or other produces into the machine. The user places a capsule, a pod of ground coffee or other portions in the machine, then presses a button to start the extraction. On the other hand, the individual packages are measured to deliver a drink, like a coffee, having the desired characteristics such as a certain strength or concentration of solids, a certain aromatic profile, a certain quantity of foam or other important attributes which characterize the drink. When the package is impermeable to gas and the coffee is kept in the package under a modified atmosphere, they retain their freshness attributes better, comparable to a freshly ground coffee, up until the actual moment of extraction. Finally, the preparation conditions, such as temperature, pressure and extraction time, can be controlled better; which provides the consumer with a relatively controlled and constant quality from one drink to another. An example of an extraction process is described in the European patent application EP 0 512 470 B1.
There is a need for a machine making it possible to provide a service in standalone or autonomous mode; that is to say which is designed to extract from capsules under pressure without necessitating a connection to the electrical power mains at the very moment of extraction. However, in order to deliver a coffee by extraction under pressure, fluid temperature and pressure conditions must be adequate.
Firstly, in order to extract from several capsules in succession, and to produce a quality drink, the temperature of the water, which passes through the capsule, must be sufficiently high, of the order of at least 90° C. for each extraction. This makes it necessary to heat the water, before it penetrates into the capsule, up to a temperature at least equal to the extraction temperature. The heating demands suitable heating means which generally consume a large amount of electrical power.
In order to deliver a drink under pressure, provision is generally made to heat a quantity of water in a circulating fluid or fast heating means such as a thermobloc and then routing this water at high pressure into the capsule; which demands a high instantaneous power in the traditional machines.
Secondly, the pressure of the fluid in the capsule must reach several bars, for example from 8 to 20 bars (of relative pressure), until the flowing of the drink. If the pressure is insufficient in the capsule, the capsule may not open if it is a capsule whose opening is related to pressure and/or the liquid cannot flow or it flows abnormally. This demands the use of a sufficiently powerful pump able to develop a static pressure of up to about 20 bars.
In an electrically autonomous (“standalone”) mode, the low voltage electrical sources, like a portable or fixed battery, are not capable of simultaneously providing this heating and the regulation of the temperature of the water associated with it and, at the same time, the pumping of the water at a sufficient pressure. Their power is normally limited because of low amperage, in such a way also as to remain within a reasonable battery weight/size range (as with a lead battery for example). In fact, the weight/size of the battery depends on the technology used. The higher the amperage, the narrower is the choice of battery technology. For high amperages, the batteries are generally heavy and not very ecological.
Moreover, for a battery of low amperage, and therefore lighter and less bulky, they do not develop power sufficiently and their autonomy under high instantaneous power is therefore very low and they therefore discharge too quickly and would not therefore be able to ensure the production of several coffees in succession.
For example, it is thus observed that it is necessary to be able to call upon a mean instantaneous power of 1400 Watt (+/−200) and a power of at least 560 Watt per hour (+/−100) in order to heat the quantity of water in a circulating fluid or fast heating means. In order to deliver an average of about 100 coffees in two hours, this requires a battery of about 120 ampere-hours. The existing batteries of this amperage value are lead batteries; they are very heavy (several kilograms), bulky and polluting.
European patent application EP 1 277 428 A1 refers to a coffee machine for a vehicle designed to extract from coffee capsules under pressure and which has a reserve of cold water, a circulating fluid water heater of the high inertia thermobloc type for heating a restricted volume of water, a pump and an extraction module supplied by the pump and in which the extraction takes place. The pumping, heating and control means are powered by the current produced by the vehicle's battery, in general a 12 volt or 24 volt battery. In order to obtain the power sufficient for the extraction process, the principle is therefore to cut off the electrical power supply or at least to greatly reduce it before operating the pump. A disadvantage arises from the waiting time between two drinks; necessary in order to heat again in the water heater the quantity necessary for the next drink. Another disadvantage arises from the high electricity consumption of the water heater which tends to exhaust the battery quickly when the engine of the vehicle is stopped. Thus, improvements in these type devices are desired.